Array - Split and join

A delimiter should be used with split method and its an optional parameter.

Syntax: 
string.split(separator, limit)


separator - Optional. Specifies the character, or the regular expression, to use for splitting the string.

limit - Optional. An integer that specifies the number of splits. No item will be take care after specified limit.

Example I:

let names = 'Test, Test1, Test3';

let arr = names.split(', ');

for (let name of arr) {
  alert( name ); // Test Test1 Test3
}

Example II:

var strTest = "How are you Baby?";
 var resTest = str.split(" ", 3);
 alert(resTest); // How,are,you

Example III:

Nothing specified then , below result you will get.

let str = "test";

alert( str.split('') ); // t,e,s,t

Join Method:

The reverse of split is called join method. Means, opposite to reverse.

let arr = ['Test1', 'Test2', 'Test3'];

let str = arr.join(';');

alert( str ); //Test1;Test2;Test3

Array Sort - Reverse

To sort an array in reverse, we can use reverse method directly. See below example,

1. Reverse an Integer array

let arr = [1, 2, 3, 4, 5];
arr.reverse();

alert( arr ); // 5,4,3,2,1

2. Reverse an string array

var fruitsTest = ["Banana", "Orange", "Apple", "Mango"];
fruitsTest.reverse();

Note: Reverse means , just reverse( End to start) the output. not any order.

Array ReOrdering - Sort

        In Javascript , the items are sorted as strings by default. So if you try to sort an array with have integer value, it will return incorrect result. See below example,

let arr = [ 1, 2, 7,15, 18 ];

arr.sort();

alert( arr );  // 1,15,18,2,7(Wrong Result)

The above example returns a wrong result. Because as I said earlier, sorted by string is default.

Remember, internally it will convert as string.

1. Classical Trick

function compareNumeric(a, b) {
  if (a > b) return 1;
  if (a == b) return 0;
  if (a < b) return -1;
}

let arr = [ 1, 2, 15, 7, 19, 54, 87, 43 ];
arr.sort(compareNumeric);
alert(arr);  // 1,2,7,15,19,43,54,87

2. With simple comparison

let arrSort = [ 1, 2, 15, 76, 76, 34, 89, 12 ];

arrSort.sort(function(a, b) { return a - b; }); // Ascending

alert(arrSort);

Note: For descending use b-a.

3. Same with Arrow function

let arrSort = [ 1, 2, 15, 76, 76, 34, 89, 12 ];

arrSort.sort( (a, b) => a - b );

alert(arrSort);

Conclusion:

Here all the example is only for integer array. Suppose If you want to sort an string array, no need to worry about above logic. Simply you can call sort method directly.

Array Reordering - map

                      This method is really very useful and often time we will use in our project.

It calls the function for each element of the array and returns the array of results. It does not change the original array.

Syntax:

let result = arr.map(function(item, index, array) {
  // returns the new value instead of item

})

item      -   The value of the current element and its mandatory.
index    -   The array index of the current element and its an optional parameter.

array    -   The array object the current element belongs to the array and its an optional.

let lengths = ["One", "Two", "Three"];
var lengthTest = lengths.map(item => item.length)
alert(lengthTest); // 3,3,5